Unexpected formation of ferrocenyl(vinyl)benzoquinoline ligands by oxidation of an alkyne benzoquinolate platinum(II) complex

Article abstract of DOI:10.1021/om4004384

Oxidation of [Pt(bzq-κN,κC¹⁰)(C₆F ₅)(η²-HC≡CFc)] (1) with PhICl₂ and I₂ affords the unusual halideferrocenyl(vinyl)benzoquinoline Pt ^II derivatives [Pt{bzq-κN-η²-CH-C(X)Fc}(C ₆F₅)X] (X = Cl (4a), I (4b)), arising from C-X and C-C coupling processes, together with small amounts of the corresponding Pt ^IV products [{Pt(bzq-κN,κC¹⁰)(C ₆F₅)X(μ-X)}₂] (X = Cl (5a), I (5b)), respectively. Complexes 4 are very stable but they undergo easy displacement reactions with PPh₃, yielding trans-[Pt(C₆F ₅)X(PPh₃)₂] and the corresponding new functionalized (vinyl)benzoquinoline ligands [(Z)-bzq-CH-C(X)Fc] (X = Cl (6a), I (6b)). The dinuclear Pt^IV derivatives 5 are alternatively obtained in high yield by oxidation of the solvate [Pt(bzq-κN,κC ¹⁰)(C₆F₅)(CH₃COCH₃)] (2). Treatment of 5 with dmso or direct oxidation of [Pt(bzq-κN,κC ¹⁰)(C₆F₅)(tht)] (3) provides mononuclear [Pt(bzq-κN,κC¹⁰)(C₆F₅)X ₂(L)] (L = dmso (7a-c), tht (8a-c)) as a mixture of cis and trans isomers.

Full text of DOI:10.1021/om4004384

Article
pubs.acs.org/Organometallics
Unexpected Formation of Ferrocenyl(vinyl)benzoquinoline Ligands
by Oxidation of an Alkyne Benzoquinolate Platinum(II) Complex
Jesus R. Berenguer, Julio Fernandez, Nora Gimenez, Elena Lalinde,* M. Teresa Moreno,
́
́
́
and Sergio Sanchez*
́
́
́
́
Departamento de Quımica-Centro de Sıntesis Quımica de La Rioja (CISQ), Universidad de La Rioja, 26006 Logrono, Spain
̃
S
* Supporting Information
ABSTRACT: Oxidation of [Pt(bzq-κN,κC10)(C6F5)(η2-
HCCFc)] (1) with PhICl2 and I2 affords the unusual
halideferrocenyl(vinyl)benzoquinoline PtII derivatives [Pt{bzq-
κN-η2-CHC(X)Fc}(C6F5)X] (X = Cl (4a), I (4b)), arising
from C−X and C−C coupling processes, together with small
amounts of the corresponding PtIV products [{Pt(bzq-
κN,κC10)(C6F5)X(μ-X)}2] (X = Cl (5a), I (5b)), respectively.
Complexes 4 are very stable but they undergo easy
displacement reactions with PPh3, yielding trans-[Pt(C6F5)X(PPh3)2] and the corresponding new functionalized (vinyl)-
benzoquinoline ligands [(Z)-bzq-CHC(X)Fc] (X = Cl (6a), I (6b)). The dinuclear PtIV derivatives 5 are alternatively obtained
in high yield by oxidation of the solvate [Pt(bzq-κN,κC10)(C6F5)(CH3COCH3)] (2). Treatment of 5 with dmso or direct
oxidation of [Pt(bzq-κN,κC10)(C6F5)(tht)] (3) provides mononuclear [Pt(bzq-κN,κC10)(C6F5)X2(L)] (L = dmso (7a−c), tht
(8a−c)) as a mixture of cis and trans isomers.
with oxidants (PhICl2 and I2). In this context, it is worth noting
that, although the mechanisms of redox transformations at
dinuclear complexes are far from being understood, the
potential of utilizing the cooperation between two centers to
allow access to new reaction pathways has been long
recognized.9,17,18
INTRODUCTION
■
Direct carbon−carbon and carbon−halogen bond formation
caused by transition metals has become a topic of tremendous
interest, owing to their importance in the design of efficient and
selective processes.1−9 In this field, significant achievements
with remarkable selectivity have been obtained via C(sp2)−H
activation of substrates having a directing group able to form
ortho-metalated complexes as initial or transient species.3,4
Among different metals, palladium and platinum complexes
have been extensively investigated in both stoichiometric and
catalytic modes in conjunction with strong oxidants (e.g.
hypervalent iodine reagents, electrophilic halogenating re-
agents, ...).5−9 In these processes, reductive elimination from
a high oxidation state (mononuclear MIV, dinuclear PdIII) has
been proposed as a key step of the carbon−carbon and
carbon−halide bond-forming reactions.5−11 Thus, in PtII
chemistry the general mechanism for the formation of new
bonds under oxidative conditions usually involves the initial
oxidation of the Pt center giving rise to a PtIV intermediate,
which undergoes subsequent reductive elimination to produce
C−C or C−halide bonds.11−13 En route, diplatinum(III)
complexes14 and even paramagnetic mononuclear PtIII species15
have been rarely found as short-lived precursors of the PtIV
intermediates. Direct attack of the electrophilic reagent at the
ligand is very rare, although some examples of fluorination,
chlorination, and bromination have been reported when the
axial site at Pt is sterically protected.16 Here we report the
synthesis of unusual (Z)-10-[1-X,1-ferrocenyl(vinyl)]-
benzoquinoline ligands (X = Cl, I) generated by simple
reaction of the alkyne complex [Pt(bzq-κN,κC10)(C6F5)(η2-
HCCFc)] (1), containing the redox-active ferrocenyl group,
Interest in platinum(II) cycloplatinated complexes contain-
ing rigid conjugated ligands such as benzo[h]quinoline has
been mainly focused on the study of their exceptional
luminescent properties with potential applications in many
areas such as light-emitting materials,19 photocatalysts,20 and
biosensors,21 and less attention has been devoted to their
reactivity.22 In the course of our current research on
luminescent benzoquinolate platinum complexes, we recently
reported the synthesis of the neutral solvate complex [Pt(bzq-
κN,κC10)(C6F5)(CH3COCH3)] (2), which allowed us to form
the alkyne derivative [Pt(bzq-κN,κC10)(C6F5)(η2-HCCFc)]
(1).23 Due to the presence of a very stable “Pt(bzq-
κN,κC10)(C6F5)” framework and two close redox centers (PtII
and FeII) connected through the unsaturated η2-alkyne unit, we
thought it could be of interest to examine its reactivity toward
halogenated sources. Halogenation reactions of mononuclear
and dinuclear PtII complexes with cyclometalated C−N ligands
have been well studied. They have shown to proceed to give
rise to both stable diplatinum species (PtIII−PtIII and PtII−
PtIV)7,14,24,25 and final PtIV complexes.26−29 However, due to
the presence of the ferrocenyl(alkyne) ligand in [Pt(bzq-
κN,κC10)(C6F5)(η2-HCCFc)] (1), its oxidation with PhICl2
Received: May 17, 2013
Published: July 5, 2013
© 2013 American Chemical Society
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Scheme 1
or I2 leads mainly to the final PtII complexes [Pt{bzq-κN-η2-
CHCFcX}(C6F5)X] (X = Cl (4a), I (4b)) containing the
new (Z)-10-[1-X,1-ferrocenyl(vinyl)] functionalized benzoqui-
noline molecules, which can be also easily obtained as the free
ligands (Z)-10-[1-X,1-ferrocenyl(vinyl)]benzoquinoline (X =
Cl (6a), I (6b)). For comparative purposes, the halogenation
reactions of the solvate precursor 2 and [Pt(bzq-κN,κC10)-
(C6F5)(tht)] (3) have been also examined, giving rise to new
pentafluorophenyl cycloplatinate PtIV derivatives.
benzoquinolate ligand in relation to the precursor (see Figure
S1 in the Supporting Information for 4b), supporting the
occurrence of a formal reduction of the alkyne unit to an olefin
with involvement of the bzq ligand. The vinyl signal exhibits in
both complexes a 2JPt−H coupling of 75 Hz, which is consistent
with η2 bonding to a PtII center.31−33 The presence of four
different CH(C5H4) proton resonances ascribed to the
ferrocenyl (Fc) group together with five distinct fluorine
resonances (2Fo, Fp, 2Fm) with 3JPt‑oF couplings in the expected
range (218−309 Hz) indicates a low symmetry with remarkable
steric congestion, leading to restricted C−Fc and PtII−
RESULTS AND DISCUSSION
■
C
ipso(C6F5) rotation in both complexes. Evaporation at room
Formation of Ferrocenyl(vinyl)benzoquinoline Sys-
tems. The complex [Pt(bzq-κN,κC10)(C6F5)(η2-HCCFc)]
(1) was found to react with 1 equiv of iodobenzene dichloride
(PhICl2) and with I2, yielding the two new types of products 4
and 5, respectively (Scheme 1). The relative proportions of
both products are dependent on the reaction temperature. In
fact, treatment of a suspension of 1 at low temperature (0 °C)
with PhICl2 yields a red solution from which only 4a is isolated
as a microcrystalline red solid. At room temperature, along with
4a, a small amount (∼12%) of 5a also precipitates as a yellow
solid. In contrast, the reactions of 1 with Cl2 (solution of Cl2 in
CCl4 or CH2Cl2) and Br2 were found to give complicated
mixtures. In the reaction with chlorine the expected 4a was only
detected (19F NMR spectroscopy) as a minor component and
5a separated out in very low yield (∼6%). Complexes 5 are
very insoluble, but they were definitively identified as dinuclear
PtIV derivatives by mass spectrometry, elemental analysis, and
IR spectroscopy. Their formation is likely due to the occurrence
of alkyne loss in solution followed by a fast attack at the Pt
center. In fact, both [{Pt(bzq-κN,κC10)(C6F5)X(μ-X)}2] (X =
Cl (5a), I (5b)) and the bromide analogue [{Pt(bzq-
κN,κC10)(C6F5)Br(μ-Br)}2] (5c) are independently obtained
by treatment of the solvate precursor [Pt(bzq-κN,κC10)(C6F5)-
(CH3COCH3)] (2) with the corresponding oxidant (PhICl2, I2,
or Br2). In this context, it should be noted that two similar
iodide dimeric complexes [Pt(phpy)ArI(μ-I)2]2 (phpy =
phenylpyridinate, Ar = C6H3Me2, C6H3(CF3)2) have recently
been reported by Yagyu et al.,30 formed by oxidative addition of
I2 to the dmso or acetonitrile precursors [Pt(phpy)Ar(S)] (S =
dmso, NCMe). Interestingly, the retention of the meridional
disposition of the phpy and Ar groups on both Pt centers was
confirmed by X-ray crystallography, and therefore, complexes 5
are suggested to have a similar structure.
temperature of a solution of 4a in a 1/2 mixture of CH2Cl2 and
n-hexane yielded red crystals suitable for X-ray crystallography.
Two molecules with identical bond lengths and angles, within
experimental error (3σ criterion), were found in the
asymmetric unit; therefore, only the data of one of them are
given here (molecule A, Figure 1, Table 1). For the data of
Figure 1. Molecular structure of [Pt{bzq-κN-η2-CHC(Cl)Fc}-
(C6F5)Cl] (4a, molecule A).
molecule B see the Supporting Information (Figure S2 and
Table S1). Both molecules are engaged by π···π interactions
associated with the bzq units, a feature not unusual with these
types of groups.23
The crystal structure reveals the formation of the new
substituted (Z)-10-[1-chloro,1-ferrocenyl(vinyl)]-
benzoquinoline, which is acting as a chelating κN:η2 ligand to
a “Pt(C6F5)Cl” fragment. In addition to the Pt−Cl bond, the
formation of the new C(vinyl)−Cl and C(bzq)−C(vinyl)
bonds implies a formal carbohalogenation of the η2-
ferrocenylacetylene, giving rise to the neutral olefin (Z)-
C(bzq)HCFcCl, in which the chlorine and Fc groups adopt
a final geminal disposition. The new carbon−chlorine (C(16)−
Complexes 4a,b have been identified as PtII complexes on the
basis of analytical data, NMR spectroscopy, and X-ray
crystallography for 4a. Their 1H NMR spectra display a
characteristic singlet of a vinyl group (δ 6.44, 4a; δ 6.46, 4b)
and distinctive downfield shifts for H2 and H9 of the
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corresponding Pt−Cipso and C−C(Fc) bonds, evident in the 1H
and 19F NMR spectra.
Table 1. Selected Distances (Å) and Angles (deg) for
Complexes
In the formation of complexes 4a,b there are several points
worth noting. First, several groups have recently developed
approaches to form diverse 10-substituted benzo[h]quinoline
molecules2,6,7,9,17,34 by metal-catalyzed C−H activation, as
effective alternatives to more traditional ortho-lithiation
electrophilic procedures, but as far as we are aware, this is
the first occasion in which an halide−vinyl fragment, CH
CXR, is incorporated. Second, the formation of the final ligands
implies a formal C−C coupling between the initial η2-alkyne
and the benzoquinolate group. In this context, we note that,
although the insertion of alkynes into cyclometalated
complexes has become an increasingly important tool for the
construction of nitrogen-containing heterocycles,3,35 the
insertion of alkynes into a benzoquinolate ligand has been
observed in only a few instances.36,37 Jones et al. have recently
reported the synthesis of an isoquinoline salt, which takes place
via an initial insertion reaction of dimethyl acetylenedicarbox-
ylate with Cp*M(bzq)Cl (M = Rh, Ir), affording the
corresponding vinyl complexes as intermediate complexes.36
A similar insertion reaction has been also reported by Cabeza et
al.37 on a triruthenium carbonyl cluster having a 2-amino-7,8-
benzoquinolate ligand and the alkynes HCCCH2X (X= OH,
SiMe3), affording in this case allyl-type η3-C3 functionalization
at the C10 site of the ligand. Third, in organoplatinum
chemistry, although migratory insertions of unsaturated
molecules such as CO, CNR, alkenes, and even alkynes into
Pt−H and Pt−R are well documented,31,33 to our knowledge a
similar insertion into the very robust Pt−C(bzq) cycloplatinate
bond has never been reported. Finally, coordination of a
terminal alkyne to a PtII complex usually makes the ligand more
electrophilic and, therefore, it is commonly involved in facile
metal-mediated nucleophilic attacks, giving new, often interest-
ing, molecules.33,38 Consequently, the observed direct reaction
of the electrophilic oxidant with the coordinated η2-alkyne,
likely mediated by the presence of the electron-rich ferrocenyl
unit, is rather striking and opens a new metal reaction pathway.
In platinum chemistry it is worth mentioning the interesting
formation of the bzqPPh2 ligand by reductive C(bzq)−P
coupling on the mixed-valence diplatinum phosphide complex
(NBu4)[PtII(C6F5)2(PPh2)2PtIV(bzq)I2],24 recently reported by
[Pt{bzq-κN-η2-CHC(Cl)Fc}(C6F5)Cl]·0.5(hexane) (4a·0.5(hexane),
molecule A)
Pt(1)−C(15)
Pt(1)−C(27)
Pt(1)−N(1)
C(16)−Cl(1)
2.098(5)
2.024(6)
2.095(4)
1.770(5)
1.485(7)
Pt(1)−C(16)
Pt(1)−Cl(2)
C(15)−C(16)
C(16)−C(17)
2.185(5)
2.3048(15)
1.398(8)
1.478(8)
C(15)−C(10)
C(27)−Pt(1)−Cl(2)
C(10)−C(15)−C(16)
C(15)−C(16)−C(17)
86.2(2)
Cl(2)−Pt(1)−N(1)
C(15)−C(16)−Cl(1)
N(1)−Pt(1)−C(27)
90.7(1)
120.0(4)
175.6(2)
129.2(5)
123.6(5)
trans-[Pt(bzq-κN,κC10)(C6F5)Br2(dmso)]·0.5(hexane) (trans-7c(dmso-
κO)·0.5(hexane))
Pt(1)−C(10)
Pt(1)−O(1)
Pt(1)−Br(1)
S(1)−O(1)
C(10)−Pt(1)−N(1)
O(1)−Pt(1)−C(15)
Br(1)−Pt(1)−C(10)
Br(1)−Pt(1)−O(1)
Br(2)−Pt(1)−C(10)
Br(2)−Pt(1)−O(1)
S(1)−O(1)−Pt(1)
2.011(6)
2.197(4)
2.4504(8)
1.544(4)
81.5(2)
92.4(2)
86.0(2)
91.1(1)
94.8(2)
87.4(1)
121.1(2)
Pt(1)−N(1)
Pt(1)−C(15)
Pt(1)−Br(2)
2.111(5)
2.050(6)
2.4654(7)
N(1)−Pt(1)−O(1)
C(10)−Pt(1)−C(15)
Br(1)−Pt(1)−N(1)
Br(1)−Pt(1)−C(15)
Br(2)−Pt(1)−N(1)
Br(2)−Pt(1)−C(15)
89.6(2)
96.8(3)
91.8(1)
93.6(2)
83.3(1)
91.4(2)
cis-[Pt(bzq-κN,κC10)(C6F5)I2(tht)] (cis-8b)
Pt(1)−C(10)
Pt(1)−S(1)
Pt(1)−I(1)
C(10)−Pt(1)−N(1)
C(10)−Pt(1)−I(1)
N(1)−Pt(1)−I(1)
C(15)−Pt(1)−I(1)
C(15)−Pt(1)−I(2)
I(1)−Pt(1)−I(2)
2.049(9)
2.386(2)
2.6479(7)
82.3(3)
84.8(2)
86.5(2)
94.6(3)
90.7(3)
95.55(2)
Pt(1)−N(1)
Pt(1)−C(15)
Pt(1)−I(2)
C(10)−Pt(1)−S(1)
N(1)−Pt(1)−S(1)
C(15)−Pt(1)−S(1)
C(15)−Pt(1)−C(10)
S(1)−Pt(1)−I(2)
N(1)−Pt(1)−I(2)
2.119(8)
2.067(9)
2.7550(7)
88.2(2)
84.9(2)
93.4(3)
92.1(4)
91.03(6)
94.9(2)
cis-[Pt(bzq-κN,κC10)(C6F5)Br2(tht)]·0.25(acetone)·0.25H2O
(8c·0.25(acetone)·0.25H2O)
Pt(1)−C(10)
Pt(1)−S(1)
Pt(1)−Br(1)
C(10)−Pt(1)−N(1)
C(10)−Pt(1)−Br(1)
N(1)−Pt(1)−Br(1)
C(15)−Pt(1)−Br(1)
C(15)−Pt(1)−Br(2)
Br(1)−Pt(1)−Br(2)
2.050(4)
2.363(1)
2.4677(5)
81.1(2)
84.6(1)
85.2(1)
92.3(2)
90.1(1)
95.25(2)
Pt(1)−N(1)
Pt(1)−C(15)
Pt(1)−Br(2)
C(10)−Pt(1)−S(1)
N(1)−Pt(1)−S(1)
C(15)−Pt(1)−S(1)
C(15)−Pt(1)−C(10)
S(1)−Pt(1)−Br(2)
N(1)−Pt(1)−Br(2)
2.112(4)
2.044(5)
2.5682(5)
96.6(1)
92.7(1)
89.8(1)
95.2(2)
83.34(3)
93.6(1)
Fortuno et al., and the serendipentious generation of [Pt(bzq-
̃
κN-η2-CCFc)(C6F5)(μ−κCα:η2-CCFc)Pt(bzq-κN,κC10)-
(C6F5)] found by slow crystallization of 1.23
Previous DFT calculations on the alkyne precursor complex
[Pt(bzq-κN,κC10)(C6F5)(η2-HCCFc)] (1) revealed that the
two highest occupied molecular orbitals are close in energy
(HOMO, −5.49 eV; HOMO-1, −5.54 eV) and are essentially
located on the ferrocenyl alkyne ligand.23 In addition, the
complex exhibits a quasi-reversible oxidation wave (see Figure
S3, Supporting Information) at 0.70 V, which is attributed to
the Fc/Fc+ redox couple. This assignment is in agreement with
previous observations on PtII cycloplatinated complexes, which
usually exhibit metal-centered irreversible waves (PtII to PtIII or
PtIV) at higher potentials.39 On these bases, although the exact
mechanism of formation of complexes 4 remains unclear, a
plausible reaction sequence illustrated with PhICl2 is presented
in Scheme 2. The reaction could be driven by initial oxidation
of the ferrocenyl group with formation of Cl• atoms and Cl−
ions giving a transient cage species of type A. Subsequent
addition of Cl• to the triple bond with a concerted associated
redox process involving Fc+ to Fc reduction and PtII to PtIV
Cl(1) = 1.770(5) Å) and carbon−carbon bond distances
(C(15)−C(10) = 1.485(7) Å) lie within the typical range
observed for single-bond distances. Although the final six-
membered ring of the chelating ligand is rather constrained, as
is evidenced by the torsion angle of 53.8(5)° between the
planes N(1)−C(12)−C(11) and C(10)−C(15)−C(16), the
olefin is essentially perpendicular to the Pt coordination plane
(87.4°), as is typical for PtII complexes.31−33 The Pt−C(olefin)
distances are relatively short (2.098(5), 2.185(5) Å), likely due
to the very low trans influence of the chloride ligand (Pt(1)−
Cl(2) = 2.3048(15) Å). These distances and the CC bond
length (1.398(8) Å) fall within the typical range of an η2-olefin
bonded to PtII.31−33 In the final complex, the C6F5 ring lies
close to the very sterically demanding ferrocenyl group, which
rationalizes the hindered rotation of these groups about the
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Scheme 2
oxidation and concomitant coordination of X− would result in
the formation of the pentacoordinated chloroferrocenyl(vinyl)
PtIV complex B. Fast isomerization of B, likely favored by the
strong trans influence of the metalated carbon atom, would give
C, which is required for the final reductive C−C coupling. The
last two steps have many precedents in PtII/PtIV systems
involving halogenated oxidants.8−13 On the other hand, the
well-known reluctance of Pt−C(C6F5) bonds to undergo
insertion and coupling processes could explain the observed
selective C−C(bzq) coupling. The regioselective formation of
the ligand (Z)-bzqCHCClFc is associated with the more
favored initial addition of the chlorine to the internal alkyne
carbon, leading to the less sterically hindered vinyl intermediate
having the two bulky groups (Fc and Cl) away from the
platinum. Although a direct electrophilic attack of X+ (Cl+ or
I+) at the electron-rich alkyne unit to afford B cannot be
completely discarded, we believe that the initial oxidation of the
Fc group promotes this attack, a fact consistent with its
electrochemical oxidation. Furthermore, the electrophilic attack
at the triple bond does not occur in the reaction between the
free HCCFc and PhICl2, which gives rise to the oxidation of
the ferrocenyl group, supporting that the first step in the
reaction is the oxidation of the Fc group in 1. Aiming to obtain
an additional insight, we also investigated the reactions of the
related alkyne complexes [Pt(bzq-κN,κC10)(C6F5)(η2-HC
benzoquinoline (X = Cl (6a), Br (6b)), which were easily
liberated from the platinum by treatment of 4a,b with an excess
of PPh3 ligand. The reactions evolve with formation of trans-
[Pt(C6F5)X(PPh3)2] complexes, as confirmed by 31P{1H} and
19F NMR spectroscopy (eq 1). After elimination of the
platinum complexes, the ligands 6a,b were isolated as pure
orange solids and fully characterized (see the Experimental
Section).
t
CR)] (R = Ph, Bu) with PhICl2. Under similar conditions, we
found that these reactions evolve slowly, generating the
insoluble diplatinum PtIV complex 5a and mixtures of more
soluble unknown species, but no signals of (vinyl)-
benzoquinoline species were observed. These results were not
unexpected, due to the lability of the alkyne ligand in solution,
and it is further evidence of the role of Fc in this
transformation.
Functionalized rigid benzoquinones are valuable molecules
due to their recognized use in photophysical applications40 and
catalysis41 and their biological42 properties. We sought to
obtain the free ligands (Z)-10-[1-X,1-ferrocenyl(vinyl)]-
The most significant feature is the olefinic proton signal,
which is seen at δ 8.31 (6a) and 8.19 (6b), respectively. These
values are in good agreement with the relatively few available
data for 10-(vinyl)benzoquinolines (δ ∼8.6),43 as expected,
shifted significantly downfield (by ca. 2 ppm) with respect to
the precursors, indicative of decoordination. The CH vinylic
carbon appears close in both ligands (δ 127.1 (6a), 126.0
(6b)), whereas the halogenated CXFc resonance exhibits the
expected tendency (δ 134.8 (6a) vs 137.3 (6b)). Crystals of
[(Z)-bzq-CHC(Cl)Fc] (6a) were obtained and subjected to
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X-ray diffraction. Although the crystal data were of moderate
quality and are not amenable for a detailed discussion, they
clearly confirmed the connectivity of the atoms and the
retention of the geometry with the geminal disposition of the
Fc and chlorine (Figure 2). Vinyl halides have found
possible, only two are observed by NMR (1H and 19F) in the
molar ratio ca. 1:1, which are ascribed to the cis(dmso-κS)
(tentatively) and trans(dmso-κO) species.
Optimization of the structures by DFT calculations for the
dichloride derivative 7a reveals that there are only small
differences in the ground state energies between the cis and the
trans isomers (see Figure S4 and Tables S2 and S3 in the
Supporting Information). From the two cis isomers, cis-
7a(dmso-κS) is slightly more stable than cis-7a(dmso-κO)
(7.2 kJ/mol), whereas the calculated energies of the two trans
isomers are approximately similar, taking into consideration the
error of the DFT calculations (trans-7a(dmso-κO) vs trans-
7a(dmso-κS) by 4.0 kJ/mol). These results are in accordance
with previous observations for similar cyclometalated PtIV
complexes with dmso ligands, which suggest that the most
favorable isomer has the oxygen atom trans to the cyclo-
metalated carbon (better σ donor and π acceptor). Similarly,
theoretical calculations have shown that the S coordination of
the dmso ligand is favored when it is in a trans disposition to an
halogen atom in PtIV complexes (in coherence with the softer
character of the S atom in relation to oxygen).27 After many
attempts, an small number of crystals of 7c were grown from
acetone/n-hexane. A single-crystal analysis stablished unambig-
uously that these crystals were the trans isomer with an oxygen-
bound dmso ligand trans to the cyclometalated carbon (Figure
3, Table 1). It is interesting that although some dmso-κO PtIV
Figure 2. Molecular structure of [(Z)-bzq-CHC(Cl)Fc] (6a).
widespread utility as substrates for a variety of cross-coupling
reactions. Therefore, the presence of chlorine or iodine in these
ligands opens the possibility of further functionalization,
allowing the synthesis of new olefinic ligands containing bzq
and Fc groups. These types of molecules would also be
expected to have potential properties as fluorescent sensor
switches, on the basis of the usual stability of the Fc/Fc+ redox
pair.44
Preparation of [Pt(bzq-κN,κC10)(C6F5)X2(L)] (L = dmso,
tht) Complexes. PtIV complexes have attracted considerable
interest, mainly because of their relevance as intermediate
species in mechanistic studies related with C−H activation and
subsequent functionalization through reductive C−X (X =
halide, C, O, N, P, ...) bond eliminations.8−13 In this context,
access to stable PtIV compounds is desirable because they will
provide further insights for understanding the reactivity of such
intermediate species. As noted above, complexes 5 are very
insoluble in usual organic solvents; however, we found that in
the strong donor solvent dmso, the dimethyl sulfoxide
molecules react with the dimers [{Pt(bzq-κN,κC10)(C6F5)X-
(μ-X)}2] (5) to give the more soluble dmso monomers
[Pt(bzq-κN,κC10)(C6F5)X2(dmso)] (7; eq 2). The reaction was
Figure 3. Molecular structure of trans-[Pt(bzq-κN,κC10)(C6F5)-
Br2(dmso-κO)] (trans-7c(dmso-κO)).
species have been proposed as intermediates in bromination
reactions in dmso solution,45 the number of crystallographically
characterized platinum complexes containing dmso-κO do-
nors27,46 are very scarce. The Pt center shows a slightly
distorted octahedral geometry with both Br atoms in a trans
disposition (Pt(1)−Br(1) = 2.4504(8) Å, Pt(1)−Br(2) =
2.4654(7) Å). The most significant distances, Pt(1)−O(1)
(2.197(4) Å) and S(1)−O(1) (1.544(4) Å), compare well with
those reported for other published examples,27 whereas the
S(1)−O(1)−Pt(1) angle (121.1(2)°) is slightly greater. The
Pt(1)−C(10) (2.011(6) Å) distance is comparable to those in
the related cis-8b and 8c. Notwithstanding, the Pt−C(C6F5)
distance (2.050(6) Å) is slightly shorter than those reported in
other reported pentafluorophenyl PtIV complexes (trans-
[Pt(C6F5)4Br(NCPh)]−, 2.106(8)−2.129(9) Å),47 due to the
low trans influence of the N donor atom.
very slow at room temperature but goes to completion upon
moderate heating (∼50 °C) in a few minutes. Treatment of the
final solution with water causes the precipitation of 7 as pale
yellow (X = Cl (7a), Br (7c)) and orange (X = I (7b)) solids,
respectively. Although the formation of different isomers is
The presence of the mixture of cis-7(dmso-κS) and trans-
7(dmso-κO) in solution is inferred from NMR spectroscopy.
Thus, at low temperature the 19F NMR spectra showed two
sets of five different signals due to C6F5 groups indicating, not
unexpectedly, restricted rotation around the Pt−C6F5 bonds in
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Figure 4. Molecular structures of (left)[cis-Pt(bzq-κN,κC10)(C6F5)I2(tht)] (cis-8b) and (right) [cis-Pt(bzq-κN,κC10)(C6F5)Br2(tht)] (8c).
1H NMR spectra of cis-8 display the characteristic H9 proton
from the bzq flanked by platinum satellites at relatively high
field (δ 7.30−7.45). This fact is indicative of shielding caused
by the proximity of this proton to the ring current of the C6F5
group and coherent with the meridional disposition of the
“Pt(C∧N)C6F5” fragment having the two carbon donors
both isomers. When the temperature was increased (see
Figures S5−S7 in the Supporting Information), for 7a,c, the
two sets of o-F and also m-F signals broaden, coalesce, and
simultaneously average into one (Tcoalescence(o-F): 293 K, 7a;
313 K, 7c), whereas for the most voluminous iodide derivative
7b four o-F are still observed at room temperature. Two sets of
bzq groups, with some of the signals overlapping, are disclosed
in the proton spectra, which supports the retention of the
meridional Pt(bzq-κN,κC10)(C6F5) unit. In particular, the
proton close to the orthometalated C (H9) appears upfield
(δ 7.32 (7a), 7.23 (cis-7b(dmso-κS)), 7.29 (trans-7b(dmso-
κO)), 7.29 (cis-7c(dmso-κS)), 7.31 (trans-7c(dmso-κO))),
indicative of strong shielding due to its proximity to the
aromatic current of the C6F5 group (Figure S8, Supporting
3
mutually cis. The lower values of JPt−H9 (8a,b, 35 Hz; 8c, 40
Hz) in comparison to that of the precursor 3 (δ 6.76, 3JPt−H9
=
62 Hz) support the coordination of the bzq to PtIV. Remarkable
steric hindrance to the rotation of the C6F5 ring is inferred from
the 19F NMR spectra, which show five distinct fluorine signals
with very different chemical environments for o-F (and also m-
F) in the range from 223 to 298 K (Figure S11, Supporting
3
Information). The observed JPt‑oF values (75−113 Hz) are
3
Information). The JPt−H values dropped considerably (35−39
typical of pentafluorophenylplatinum(IV) complexes,47−49
showing an important decrease with respect to the values
found in complexes 123 and 350 (∼510 Hz).
Hz) in relation to the precursors 1 and 2 (∼70 Hz), which is
consistent with the change from PtII to PtIV. At room
temperature, the methyl resonances of the dmso ligand in
both isomers are found as well-separated singlet resonances
(broad in cis-7b(dmso-κS)), remarkably more deshielded in
the cis-7(dmso-κS) isomers (3.05−3.07 ppm) than in the
trans-7(dmso-κO) isomers (2.53−2.55 ppm), a feature that has
been previously observed in related PtIV complexes featuring O-
and S-bound dmso.45 Upon cooling, the resonance due to cis-
κS broadens and finally splits into the expected two distinct
singlets (δ 3.09, 3.03 (7a), 3.16, 2.99 (7b), 3.15, 3.01 (7c)),
while the singlet due to the trans-7(dmso-κO) isomers remains
unchanged. Unfortunately, no satellites were observed in any of
the methyl signals. Confirmation of the κS coordination of the
dmso ligand in the cis isomers was obtained by a sequence of
NOESY and NOE experiments between the H2 proton of the
bzq and the Me resonances of the dmso (Figures S9 and S10
(Supporting Information) for 7c). The lack of NOE coupling
between the methyl and the aromatic H2 protons for the
second isomer confirms that the dmso is coordinated through
the oxygen atom. Interestingly, though the ratio between both
isomers does not change noticeably once they are formed, we
observed that increasing the reaction time in dmso leads always
to higher proportions of trans-7(dmso-κO). By way of
comparison, the oxidation reactions of [Pt(bzq-κN,κC10)-
(C6F5)(tht)] (3) with PhICl2, I2, and Br2 were also examined.
These reactions evolve with retention of the meridional
disposition of the “Pt(bzq-κN,κC10)(C6F5)” fragment and
formation of [Pt(bzq-κN,κC10)(C6F5)X2(tht)] (8a−c) as a cis
derivative (8c) or a mixture of cis and trans isomers, (cis:trans ≈
7:1 (8a) 5:1 (8b)) (eq 3), from which the cis isomers can be
separated as pure complexes by crystallization. As expected, the
Slow diffusion of n-hexane into chloroform or acetone
solutions of the cis isomers 8b,c, respectively, produced X-ray-
quality crystals (Figure 4).
Remarkably, a search of the Cambridge Crystallograpic
Database reveals that, although tht is a common ligand for PtII
complexes, there is only one reported crystal structure of a PtIV
derivative.51 Both structures (cis-8b and cis-8c) are similar and
confirm that the bzq and C6F5 groups retain the meridional
disposition of the precursor. The platinum shows a distorted-
octahedral geometry of a PtIV complex with both iodide (8b)
and bromide (8c) atoms in a mutually cis disposition and bond
distances and angles (Table 1) in the usual range observed in
other PtIV derivatives with the same ligands.13,28−30,52 In both
compounds, the Pt−X distance trans to the tetrahydrothio-
phene ligand (Pt(1)−I(1) = 2.6479(7) Å and Pt(1)−Br(1) =
2.4677(5) Å) is remarkably shorter than the distance trans to
the C(bzq) metalate carbon (Pt(1)−I(2) = 2.7550(7) Å and
Pt(1)−Br(2) = 2.5682(5) Å), in agreement with the lower trans
influence of the sulfur atom. As expected, the Pt−C (2.044(5)−
2.067(9) Å) and Pt−N (2.119(8), 2.112(4) Å) distances are
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Ag/AgCl reference electrode) on a Voltalab PST 050 instrument. The
ferrocene/ferrocenium couple served as internal reference (+0.46 V vs
Ag/AgCl). 7,8-Benzo[h]quinoline (Hbzq) was purchased from Sigma-
Aldrich, and [Pt(bzq-κN,κC10)(C6F5)(η2-HCCFc)],23 [Pt(bzq-
κN,κC10)(C6F5)(CH3COCH3)],23 and [Pt(bzq-κN,κC10)(C6F5)-
(tht)]50 were prepared as reported previously.
longer than those reported recently for the precursor 3 (Pt−C
= 2.000(7)−2.003(8) Å, Pt−N = 2.078(7) Å), which is
consistent with the increase in the coordination number. The
Pt−C(C6F5) distances (8b, 2.067(9) Å; 8c, 2.044(5) Å) are
slightly shorter than those reported in other pentafluorophenyl
PtIV complexes,47 due to the very low trans influence of the N
donor atom. Along the same line, the Pt−S bond lengths
(2.386(2), 2.363(1) Å) do not deviate significantly from that
seen in 3 (2.3719(19) Å).50 This fact can also be attributed to
the nature of the trans ligands. The lower trans influence of the
halide in the PtIV species 8 in relation to that of C(bzq) in the
PtII species 3 is balancing the change in oxidation state.
Preparation of [Pt{bzq-κN-η2-CHC(Cl)Fc}(C6F5)Cl] (4a). To a
suspension of [Pt(bzq-κN,κC10)(C6F5)(η2-HCCFc)] (1; 0.200 g,
0.266 mmol) in CH2Cl2 (20 mL) at 0 °C was added iodobenzene
dichloride (0.073 g, 0.266 mmol). The mixture was stirred for 3 h, and
the obtained red solution was evaporated to dryness. Treatment of the
residue with n-hexane (5 mL) afforded 4a as a red solid (0.172 g,
79%).
When the reaction was carried out at 298 K during 3 h, a pale
yellow solid precipitated and was identified as [{Pt(bzq-κN,κC10)-
(C6F5)Cl(μ-Cl)}2] (5a) and separated by filtration (0.019 g, 12%).
The red filtrate was evaporated to dryness and treated with n-hexane
(5 mL) to give 4a (0.129 g, 59%). IR (cm−1): ν(CC) 1373 (s);
ν(C6F5)X‑sens 809 (m). Anal. Calcd for C31H18Cl2F5FeNPt: C, 45.33;
H, 2.21; N 1.71. Found: C, 45.06; H, 2.18; N, 1.67. MALDI-TOF (+):
m/z (%) 821 [M]+ (52); 786 [M − Cl]+ (40). 1H NMR (400.1 MHz,
CDCl3, 20 °C, δ): 9.79 (d, J = 4.7 H2, bzq), 8.50 (d, J = 6.4, H4, bzq),
8.15 (d, J = 7.7, H7, bzq), 8.01 (m, 2H, H9, H5,6, bzq), 7.89 (t, J = 7.7,
H8, bzq), 7.80 (d, J = 8.7, H5,6, bzq), 7.74 (dd, J = 7.8, J = 5.0, H3, bzq),
On the basis of literature precedents for analogous oxidation
reactions of PtII complexes with halogenated oxidants, we
propose that the first step is a two-electron oxidation to form a
cationic PtIV intermediate, followed by reaction with X− to yield
the final complexes.8−13,28,47−49 It should be noted that a
rearrangement of the pentacoordinate species is required to
render the final cis isomers. Similar isomerizations have been
previously observed.8−11,48 The preference for the cis isomer,
which locates the sulfur cis to the metalate C(bzq) carbon atom,
is in accordance with the so-called “transphobia” effect.53
3
6.44 (s, JPt−H = 75, 1H, bzq-CHCFcCl), 4.85 (s, 1H, C5H4), 4.47
(s, 1H, C5H4), 4.02 (s, 5H, Cp), 3.97 (s, 1H, C5H4), 3.63 (s, 1H,
C5H4). 19F NMR (282.4 MHz, CDCl3, 20 °C, δ): −119.7 (d, JPt‑oF
=
CONCLUDING REMARKS
■
218, 1o-F), −126.5 (d, JPt‑oF = 305, 1o-F), −161.1 (t, 1p-F), −163.2
(m, 1m-F), −164.2 (m, 1m-F). E1/2 = 0.67 V (vs Ag/AgCl).
In summary, we have disclosed that the oxidation of the
ferrocenyl group in the η2-ferrocenyl alkyne complex [Pt(bzq-
κN,κC10)(C6F5)(η2-HCCFc)] (1) induces a formal electro-
philic addition to the unsaturated alkyne with concomitant C−
C bond formation, thus forming the final PtII complexes
[Pt{bzq-κN-η2-CHC(X)Fc}(C6F5)X] (4). The new func-
tionalized (vinyl)benzoquinoline ligands can be easily liberated
from metal by a displacement reaction with PPh3. These results
reveal a novel reactivity pattern in both the well-known PtIV/
PtII redox systems and in the usual reactivity of alkynes in
platinum chemistry and illustrate the potential of utilizing the
cooperation between two redox centers to allow access to new
reaction pathways.
Preparation of [Pt{bzq-κN-η2-CHC(I)Fc}(C6F5)I] (4b). To a
suspension of [Pt(bzq-κN,κC10)(C6F5)(η2-HCCFc)] (0.170 g,
0.227 mmol) in CH2Cl2 (20 mL) was added 0.058 g of I2 (0.227
mmol) at 25 °C. After 3 h of stirring, the orange solid that precipitated
was filtered and indentified as [{Pt(bzq-κN,κC10)(C6F5)I(μ-I)}2] (5b;
0.042 g, 23%). The red filtrate was evaporated to dryness and treated
with n-hexane (5 mL) to give 4b as a maroon solid (0.101 g, 44%). At
0 °C, 5b and 4b were also isolated in 50% and 27% yields, respectively.
IR (cm−1): ν(CC) 1377 (m), ν(C6F5)X‑sens 805 (m). Anal. Calcd for
C31H18I2F5FeNPt: C, 37.08; H, 1.81; N 1.39. Found: C, 36.99; H,
1.78; N, 1.27. MALDI-TOF (+): m/z (%) 1004 [M]+ (100), 750 [M
+
1
− I2] (18). H NMR (300.1 MHz, CDCl3, 20 °C, δ): 10.10 (d, J =
5.0, H2, bzq), 8.52 (d, J = 7.8, H4, bzq), 8.15 (d, J = 7.1, H7, bzq), 8.03
(d, J = 8.7, H5,6, bzq), 7.89 (m, 2H, H8, H9, bzq), 7.79 (d, J = 8.7, H5,6,
Furthermore, the study of related oxidation reactions using as
precursors the labile substrates [Pt(bzq-κN,κC10)(C6F5)(η2-
HCCPh)], [Pt(bzq-κN,κC10)(C6F5)(CH3COCH3)] (2), or
[Pt(bzq-κN,κC10)(C6F5)(tht)] (3) has allowed us to prepare
new benzoquinolatepentafluorophenyl PtIV complexes (5, 7,
and 8), which could be relevant for understanding mechanistic
processes or as precursors to develop novel d6 luminescent
materials.
3
bzq), 7.73 (t, J = 9.6, H3, bzq), 6.46 (s, JPt−H = 75, 1H, bzq-CH
CFcI), 4.75 (s, 1H, C5H4), 4.48 (s, 1H, C5H4), 4.07 (s, 5H, Cp), 4.02
(s, 1H, C5H4), 3.86 (s, 1H, C5H4). 19F NMR (282.4 MHz, CDCl3, 20
°C, δ): −115.9 (d, JPt‑oF = 223, 1o-F), −125.5 (d, JPt‑oF = 309, 1o-F),
−161.2 (t, 1p-F), −163.7 (m, 1m-F), −164.7 (m, 1m-F). E1/2 = 0.69 V
(vs Ag/AgCl).
Preparation of [{Pt(bzq-κN,κC10)(C6F5)X(μ-X)}2] (X = Cl (5a), I
(5b), Br (5c)). To a solution of [Pt(bzq-κN,κC10)(C6F5)-
(CH3COCH3)] (2) in CH2Cl2 (15 mL) at 0 °C was added 1 equiv
of the corresponding oxidant (PhICl2, I2, and Br2, respectively). After 3
h of stirring, the suspension that was obtained was filtered, giving 5 as
pale yellow (5a), red (5b), and orange (5c) solids. As noted above, the
complexes [{Pt(bzq-κN,κC10)(C6F5)X(μ-X)}2] (X = Cl (5a), I (5b))
can be alternatively synthesized in low yield (12% (5a), 23% (5b)) by
reaction of [Pt(bzq-κN,κC10)(C6F5)(η2-HCCFc)] (1) and the
corresponding oxidant (PhICl2 (5a), I2 (5b)) at 25 °C.
EXPERIMENTAL SECTION
■
General Comments. All reactions were carried out under an
atmosphere of dry argon, using standard Schlenk techniques. Solvents
were obtained from a solvent purification system (M-BRAUN MB
SPS-800). NMR spectra were recorded at 293 K on a Bruker ADX 400
spectrometer. Chemical shifts are reported in ppm relative to external
standards (SiMe4, CFCl3), and all coupling constants are given in Hz.
The NMR spectral assignments of the benzoquinolate ligand (bzq)
follow the numbering scheme shown in Figure S12 (Supporting
Information). IR spectra were obtained on a Nicolet Nexus FT-IR
spectrometer, using Nujol mulls between polyethylene sheets.
Elemental analyses were carried out with Perkin-Elmer 2400
CHNS/O and Carlo Erba EA1110 CHNS-O microanalyzers. Mass
spectra were recorded on a Microflex MALDI-TOF Bruker (MALDI)
spectrometer operating in the linear and reflector modes using
dithranol as matrix. Cyclic voltammetry was carried out in 0.1 M
NBu4PF6 solutions as supporting electrolyte, using a three-electrode
configuration (Pt disk as working electrode, Pt-wire counter electrode,
Data for [{Pt(bzq-κN,κC10)(C6F5)Cl(μ-Cl)}2] (5a). [Pt(bzq-κN,κC10)-
(C6F5)(CH3COCH3)] (2; 0.100 g, 0.167 mmol) and iodobenzene
dichloride (PhICl2, 0.046 g, 0.167 mmol) were used (yield of 5a: 0.063
g, 61%). IR (cm−1): ν(C−F) 1075 (s), 969 (s); ν(C)X‑sens 800 (s);
ν(Pt−Cl) 367 (m), 306, 300 (w). Anal. Calcd for C38H16Cl4F10N2Pt2:
C, 37.33; H, 1.32; N 2.29. Found: C, 37.02; H, 1.25; N, 1.98. MALDI-
TOF (+): m/z (%) 1221 [M]+ (1), 1187 [M − Cl]+ (33), 826
[Pt2Cl(bzq)2]+ (100). 1H NMR (400.1 MHz, dmso-d6, 20 °C, δ): 9.22
(dd, J = 5.3, J = 1.0, 3JPt−H = 19, H2, bzq), 8.77 (dd, J = 8.1, JH−H = 1.1,
H4, bzq), 8.07−7.94 (m, H3, H5, H6, bzq), 7.75 (d, J = 7.8, H7, bzq),
3
7.51 (t, J = 7.8, H8, bzq), 7.12 (d, J = 7.8, JPt−H = 35, H9, bzq). 19F
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NMR (282.4 MHz, dmso-d6, 20 °C, δ): −114.2 (s, br, 2o-F), −158.5
(t, 1p-F), −162.8 (m, 2m-F); at 55 °C, −113.8 (s, 2o-F), −159.4 (t,
1p-F), −163.6 (m, 2m-F).
0.57 V (vs Ag/AgCl) (more waves due to electrogenerated by
products are seen at higher potentials).
Preparation of [Pt(bzq-κN,κC10)(C6F5)X2(dmso)] (X = Cl (7a), I
(7b), Br (7c)). General Procedure. A suspension of [{Pt(bzq-
κN,κC10)(C6F5)X(μ-X)}2] (5) in 2 mL of dmso was heated to 50 °C
for 5 min and stirred until complete dissolution of the corresponding
complex. The solution was poured into 400 mL of H2O, and the
obtained precipitate was filtered to give 7.
Data for [{Pt(bzq-κN,κC10)(C6F5)I(μ-I)}2] (5b). [Pt(bzq-κN,κC10)-
(C6F5)(CH3COCH3)] (2; 0.100 g, 0.167 mmol) and I2 (0.042 g,
0.167 mmol) were used (yield of 5b: 0.107 g, 80%). IR (cm−1): ν(C−
F) 1071 (s), 967 (s); ν(C6F5)X‑sens 792 (m), 770 (m); ν(Pt−I) 225
(w), 220 (w). Anal. Calcd for C38H16I4F10N2Pt2: C, 28.74; H, 1.02; N,
1.76. Found: C, 28.56; H, 0.98; N, 1.46. MALDI-TOF (+): m/z (%)
Data for [Pt(bzq-κN,κC10)(C6F5)Cl2(dmso)] (7a). Starting from
[{Pt(bzq-κN,κC10)(C6F5)Cl(μ-Cl)}2] (5a; 0.050 g, 0.041 mmol), 7a
was obtained as a pale yellow solid (0.046 g, 82%). IR (cm−1): ν(C−
F) 1073 (s), 970 (s); ν(C6F5)X‑sens 798 (m); ν(Pt−Cl) 349 (m), 325
(w). Anal. Calcd for C21H14Cl2F5NOPtS: C, 36.59; H, 2.05; N, 2.03; S,
4.65. Found: C, 36.10; H, 2.19; N, 2.26; S, 3.97. MALDI-TOF (−):
m/z (%) 646 [M − dmso + Cl]− (100), 610 [M − dmso]− (35), 576
1
1461 [M − I]+ (9). H NMR (400.1 MHz, dmso-d6, 20 °C, δ): 9.26
(d, J = 5.6, JPt−H = 20, H2, bzq), 8.69 (d, J = 7.9, H4, bzq), 8.01 − 7.94
(m, H3, H5, H6, bzq), 7.57 (d, J = 7.7, H7, bzq), 7.50 (t, J = 7.7, H8,
3
bzq), 7.08 (dd, J = 7.7, JPt−H = 36, H9, bzq). 19F NMR (282.4 MHz,
dmso-d6, 20 °C, δ): −99.5 (s, 1o-F), −104.7 (s, 1o-F), −159.2 (t, 1p-
F), −162.3 (m, 1m-F), −163.7 (m, 1m-F).
1
[Pt(bzq)(C6F5)Cl]− (62). H NMR (400.1 MHz, CD3COCD3, −30
Data for [{Pt(bzq-κN,κC10)(C6F5)Br(μ-Br)}2] (5c). [Pt(bzq-κN,κC10)-
(C6F5)(CH3COCH3)] (2; 0.100 g, 0.167 mmol) and Br2 (9 μL, 0.167
mmol) were used (5c: 0.087 g, 74%). IR (cm−1): ν(C−F) 1074 (s),
967 (s); ν(C6F5)X‑sens 795 (s); ν(Pt−Br) 268 (m), 248, 234 (m). Anal.
Calcd for C38H16Br4F10N2Pt2: C, 32.67; H, 1.16; N, 2.01. Found: C,
32.05; H, 1.31; N, 2.00. MALDI-TOF (+): m/z (%) 1321 [M − Br]+
(22). 1H NMR (400.1 MHz, dmso-d6, 20 °C, δ): 9.29 (d, J = 5.2, JPt−H
= 19, H2, bzq), 8.81 (d, J = 7.9, H4, bzq), 8.01 − 7.94 (m, H3, H5, H6,
bzq), 7.75 (d, J = 7.8, H7, bzq), 7.58 (t, J = 7.7, H8, bzq), 7.16 (m,
3JPt−H = 38.9, H9, bzq). 19F NMR (282.4 MHz, dmso-d6, 20 °C, δ):
−107.3 (s, br, 1o-F), −112.3 (s, br, 1o-F), −159.0 (t, 1p-F), −163.1
(m, 2m-F).
°C, cis:trans isomers ∼1:1.5, δ): cis-7a(dmso-κS) 9.42 (d, J = 5.0, H2,
bzq), 8.81 (d, J = 8.6, H4, bzq), 8.10 (m, 3H, H5, H6, H3, bzq), 7.82 (t,
J = 8.0, H8, bzq), 7.59 (d, J = 7.3, H7, bzq), 7.32 (t, J = 8.4, JPt−H = 39,
H9, bzq), 3.09 (s, 3H, CH3, dmso), 3.03 (s, 3H, CH3, dmso); trans-
7a(dmso-κO) 9.40 (d, J = 5.1, H2, bzq), 8.85 (d, J = 8.1, H4, bzq),
8.15−8.04 (m, 3H, H5, H6, H3, bzq), 7.82 (t, J = 8.0, H8, bzq), 7.59 (d,
J = 7.3, H7, bzq), 7.32 (t, J = 8.4, J
= 39, H9, bzq), 2.54 (s, 6H,
Pt−H
dmso). When the temperature was increased, the two Me signals of
the cis isomer broadened and averaged into one at 3.05 ppm. 19F NMR
(376.5 MHz, CD3COCD3, −50 °C, δ): cis-7a(dmso-κS) −112.2 (d,
JPt‑oF = 102, 1o-F), −119.0 (d, JPt‑oF = 105, 1o-F), −160.8 (t, 1p-F),
−164.1 (m, 1m-F), −165.1 (m, 1m-F); trans-7a(dmso-κO) −112.6 (d,
JPt‑oF = 104, 1o-F), −117.6 (d, JPt‑oF = 116, 1o-F), −161.0 (t, 1p-F),
−164.4 (m, 1m-F), −166.0 (m, 1m-F). 19F NMR (25 °C, δ): −115.0
(br), −161.6 (t, p-F, trans), −161.9 (t, p-F, cis), −165.5 (m, br, m-F,
trans), −165.9 (m, br, m-F, cis).
Preparation of [bzq-CHC(Cl)Fc] (6a). To a cooled (0 °C)
solution of [Pt{bzq-κN-η2-CHC(Cl)Fc}(C6F5)Cl] (4a; 0.129 g,
0.157 mmol) in CH2Cl2 (20 mL) was added 2 equiv of
triphenylphosphine (0.082 g, 0.314 mmol). After 1 h of stirring, the
solvent was removed and the residue treated with Et2O (20 mL),
giving a solid which was filtered and identified as trans-[Pt(C6F5)Cl-
(PPh3)2] (0.040 g, 28%). The orange filtrate was concentrated to a
small volume (2 mL) and purified by column chromatography (SiO2,
n-hexane/CH2Cl2 8/2) to give 6a as an orange solid (0.021 g, 32%).
IR (cm−1): ν(CC) 1374 (s). MALDI-TOF (+): m/z (%) 423 [M]+
(100). Anal. Calcd for C25H18ClFeN: C, 70.87; H, 4.28; N, 3.31.
Data for [Pt(bzq-κN,κC10)(C6F5)I2(dmso)] (7b). Starting from
[{Pt(bzq-κN,κC10)(C6F5)I(μ-I)}2] (5b; 0.040 g, 0.025 mmol), 7b
was obtained as an orange solid (0.039 g, 88%). IR (cm−1): ν(C−F)
1066 (m), 967 (m); ν(C6F5)X‑sens 791 (m); ν(Pt−I) 247 (w), 224 (w).
Anal. Calcd for C21H14I2F5NOPtS: C, 28.92; H, 1.62; N, 1.61; S, 3.68.
Found C, 28.39; H, 0.97; N, 1.71; S, 3.08. MALDI-TOF (−): m/z (%)
667 [Pt(bzq)(C6F5)I]− (100). MALDI-TOF (+): m/z (%) 744 [M −
I]+ (17). 1H NMR (400.1 MHz, CD3COCD3, −50 °C, cis:trans
isomers ∼1:1, δ): cis-7b(dmso-κS) 9.47 (d, J = 6.0, H2, bzq), 8.75 (d, J
= 8.1, H4, bzq), 8.15−8.05 (m, 3H, H5, H6, H3, bzq), 7.66−7.57 (m,
1
Found: C, 70.41; H, 3.89; N, 3.52. H NMR (400.1 MHz, CDCl3, 20
°C, δ): 9.12 (dd, J = 4.2, J = 1.6, H2, bzq), 8.31 (s, 1H, bzq-CH
CFcCl), 8.19 (d, J = 8, H4, bzq), 7.96 (d, J = 7.9, H7/9, bzq), 7.92 (d, J
= 7.9, H7/9, bzq), 7.85 (d, J = 8.8, H5/6, bzq), 7.73 (t, J = 7.9, H8, bzq),
7.70 (d, J = 8.8, H5/6, bzq), 7.53 (dd, J = 4.2, J = 8.1, H3, bzq), 4.83 (s,
2H, C5H4), 4.36 (s, 2H, C5H4), 4.30 (s, 5H, Cp). 13C{1H} NMR
(100.6 MHz, CDCl3, 20 °C, δ): 148.0 (s, C12, bzq), 147.5 (s, C2, bzq),
135.5 (s, C4, bzq), 134.8 (s, =C(Cl)Fc), 131.2 (s, C7/9, bzq), 129.2 (s,
bzq), 128.7 (s, C5/6, bzq), 128.0 (s, C7/9, bzq), 127.7 (s, bzq), 127.3 (s,
C8, bzq), 127.1 (s, CHC(Cl)Fc), 126.7 (s, bzq), 125.6 (s, C5/6, bzq),
121.1 (s, C3, bzq), 69.7 (s, 5C, Cp), 69.1 (s, 2C, C5H4), 67.3 (s, 2C,
C5H4). E1/2 = 0.55 V (vs Ag/AgCl) (more waves due to
electrogenerated by products are seen at higher potentials).
2H, H7, H8, bzq), 7.23 (d, J = 7.5, J
= 37, H9, bzq), 3.16 (s, 3H,
Pt−H
CH3, dmso), 2.99 (s, 3H, CH3, dmso); trans-7b(dmso-κO) 9.44 (d, J
= 5.1, H2, bzq), 8.78 (d, J = 8.0, H4, bzq), 8.15−8.05 (m, 3H, H5, H6,
H3, bzq), 7.66−7.57 (m, 2H, H7, H8, bzq), 7.29 (d, J = 7.2, JPt−H = 39,
H9, bzq), 2.53 (s, 6H, CH3, dmso). When the temperature was
increased, the two Me signals of the cis isomer broadened and averaged
into one at 3.06 ppm. 19F NMR (376.5 MHz, CD3COCD3, −50 °C,
δ): cis-7b(dmso-κS) −100.2 (d, JPt‑oF = 111, 1o-F), −106.4 (d, JPt‑oF
122, 1o-F), −160.9 (t, 1p-F), −163.7 (m, 1m-F), −165.1 (m, 1m-F);
trans-7b(dmso-κO) −101.1 (d, JPt‑oF = 107, 1o-F), −105.1 (d, JPt‑oF
=
=
Preparation of [bzq-CHC(I)Fc] (6b). Following the same
procedure as that for 6a, starting from [Pt{bzq-κN-η2-CHC(I)Fc}-
(C6F5)I] (4b; 0.093 g, 0.093 mmol) and PPh3 (0.049 g, 0.186 mmol),
6b was obtained as an orange solid after purification by column
chromatography (SiO2, n-hexane/CH2Cl2 8/2) (0.014 g, 29%). IR
(cm−1): ν(CC) 1374 (s). MALDI-TOF (+): m/z (%) 515 [M]+
(82), 388 [M − I]+ (100). Anal. Calcd for C25H18IFeN: C, 58.29; H,
126, 1o-F), −161.2 (t, 1p-F), −164.1 (m, 1m-F), −165.9 (m, 1m-F).
19F NMR (25 °C, δ): −99.5 (s, br, o-F, cis), −100.7 (s, br, o-F, trans),
−161.9 (t, p-F, cis + trans), −164.8 (m, br, m-F, cis + trans), −166.0,
−166.4 (m, br, m-F, cis + trans).
Data for [Pt(bzq-κN,κC10)(C6F5)(dmso)Br2] (7c). Starting from
[{Pt(bzq-κN,κC10)(C6F5)Br(μ-Br)}2] (5c; 0.050 g, 0.036 mmol), 7c
was obtained as a pale yellow solid (0.044 g, 79%). IR (cm−1): ν(C−
F) 1077 (m), 971 (m); ν(C6F5)X‑sens 793 (m); ν(Pt−Br) 268 (w), 232
(w). Anal. Calcd for C21H14Br2F5NOPtS: C, 32.41; H, 1.81; N, 1.80; S,
4.12. Found: C, 32.13; H, 1.51; N, 2.32; S, 3.75. MALDI-TOF (−):
m/z (%) 779 [M]− (25), 770 [M − dmso]− (10), 620 [M − dmso −
1
3.52; N, 2.72. Found: C, 57.91; H, 3.29; N, 2.51. H NMR (400.1
MHz, CD3COCD3, 20 °C, δ): 9.16 (dd, J = 4.3, J = 1.4, H2, bzq), 8.39
(d, J = 8.1, H4, bzq), 8.19 (s, 1H, bzq-CHCFcI), 8.05 (m, H8, bzq),
7.98 (d, J = 8.7, H5/6, bzq), 7.86 (d, J = 8.7, H5/6, bzq), 7.78−7.73 (m,
2H, H7, H9, bzq), 7.67 (m, H3, bzq), 4.86 (s, 2H, C5H4), 4.44 (s, 2H,
C5H4), 4.31 (s, 5H, Cp). 13C{1H} NMR (100.6 MHz, CD3COCD3, 20
°C, δ) 148.5 (s, C12, bzq), 147.9 (s, C2, bzq), 137.3 (s, =C(I)Fc), 135.8
(s, C4, bzq), 131.2 (s, C7/9, bzq), 130.5 (s, bzq), 128.4 (s, C5/6, bzq),
128.3 (s, C8, bzq), 127.1 (s, C7/9, bzq), 126.8 (s, bzq), 126.0 (s, CH
C(I)Fc), 125.8 (s, C5/6, bzq), 123.5 (s, bzq), 121.5 (s, C3, bzq), 69.7
1
Br]− (100). H NMR (400.1 MHz, CD3COCD3, −50 °C, cis:trans
isomers ∼2:1, δ): cis-7c(dmso-κS) 9.46 (d, J = 5.2, JPt−H = 18, H2,
bzq), 8.82 (d, J = 7.8, H4, bzq), 8.08 (m, 3H, H3, H5, H6, bzq), 7.76 (d,
J = 8.0, H7, bzq), 7.59 (t, J = 8.0, H8, bzq), 7.29 (d, J = 7.1, JPt−H = 35,
H9, bzq), 3.15 (s, 3H, CH3, dmso), 3.01 (s, 3H, CH3, dmso); trans-
7c(dmso-κO) 9.42 (d, J = 5.2, JPt−H = 17, H2, bzq), 8.85 (d, J = 7.9,
H4, bzq), 8.17 (t, J = 5.5, H3, bzq), 8.16 (m, H5, H6, bzq), 7.77 (d, J =
(s, 5C, Cp, Fc), 69.3 (s, 2C, C5H4, Fc), 68.9 (s, 2C, C5H4, Fc). E1/2
=
3950
dx.doi.org/10.1021/om4004384 | Organometallics 2013, 32, 3943−3953

Organometallics
Article
7.9, H7, bzq), 7.60 (m, H8, bzq), 7.31 (d, J = 7.9, J Pt−H = 36, H9, bzq),
2.55 (s, 6H, CH3, dmso). When the temperature was increased, the
two Me signals of the cis isomer broadened and averaged into one at
3.07 ppm. 19F NMR (376.5 MHz, CD3COCD3, −50 °C, δ): cis-
7c(dmso-κS) −107.8 (d, JPt‑oF = 108, 1o-F), −114.4 (d, JPt‑oF = 114,
1o-F), −160.7 (t, 1p-F), −163.9 (m, 1m-F), −165.1 (m, 1m-F); trans-
7c(dmso-κO) −108.3 (d, JPt‑oF = 108, 1o-F), −112.9 (d, JPt‑oF = 113,
1o-F), −160.9 (t, 1p-F), −164.2 (m, 1m-F), −165.9 (m, 1m-F). 19F
NMR (25 °C, δ): −108.0 (br, o-F), −112.6 (br, o-F), −161.8 (t, p-F,
cis+trans), −165.6 (m, br, m-F, cis + trans).
Data for [Pt(bzq-κN,κC10)(C6F5)Br2(tht)] (8c). [Pt(bzq-κN,κC10)-
(C6F5)(tht)] (3; 0.136 g, 0.216 mmol) and Br2 (11 μL, 0.216 mmol)
were used to obtain cis-8c as a yellow solid (0.080 g, 47%). IR (cm−1):
ν(C−F) 1074 (s), 974 (s); ν(C6F5)X‑sens 791 (s); ν(Pt−Br) 234 (w).
Anal. Calcd for C23H16Br2F5NPtS: C, 35.04; H, 2.05; N, 1.78; S, 4.07.
Found: C, 34.84; H, 2.26; N, 2.18; S, 4.35. MALDI-TOF (+): m/z (%)
790 [M]+ (30), 710 [M − Br]+ (100). 1H NMR (400.1 MHz,
CD3COCD3, 25 °C, δ): 10.00 (d, J = 8, JPt−H = 18, H2, bzq), 8.87 (d, J
= 8.1, H4, bzq), 8.13 (m, 2H, H3, H5/6, bzq), 8.05 (d, J = 8.0, H5/6
,
bzq), 7.90 (d, J = 7.8, H7, bzq), 7.69 (t, J = 7.8, H8, bzq), 7.42 (t, J =
7.8, JPt−H = 40, H9, bzq), 3.13 (m, 1H, α-CH2, tht), 3.06 (m, 1H, α-
CH2, tht), 2.20 (m, 1H, α-CH2, tht), 1.80 (m, 1H, α-CH2, tht), 1.77
(m, 1H, β-CH2, tht), 1.57 (m, 1H, β-CH2, tht), 1.04 (m, 1H, β-CH2,
tht), 0.97 (m, 1H, β-CH2, tht). 19F NMR (376.5 MHz, CD3COCD3,
−50 °C, δ): −103.3 (d, JPt‑oF = 87, 1o-F), −115.5 (d, JPt‑oF = 90, 1o-F),
−160.3 (t, 1p-F), −164.0 (m, 1m-F), −164.7 (m, 1m-F).
Preparation of [Pt(bzq-κN,κC10)(C6F5)X2(tht)] (X = Cl (8a), I
(8b), Br (8c)). General Procedure. To a solution of [Pt(bzq-
κN,κC10)(C6F5)tht] (3) in CH2Cl2 1 equiv of the corresponding
oxidant (PhICl2, I2, or Br2) was added. After 1 h of reaction, the
solvent was evaporated to dryness and the residue was treated with
Et2O (5 mL) obtaining 8.
Data for [Pt(bzq-κN,κC10)(C6F5)Cl2(tht)] (8a). [Pt(bzq-κN,κC10)-
(C6F5)(tht)] (3; 0.140 g, 0.223 mmol) and PhICl2 (0.061 g, 0.223
mmol) were used to give 8a as a pale yellow solid (0.120 g, 77%). IR
(cm−1): ν(C−F) 1079 (s), 967 (s); ν(C6F5)X‑sens 796 (s); ν(Pt−Cl)
348 (s), 345 (w). Anal. Calcd for C23H16Cl2F5NPtS: C, 39.50; H, 2.31;
N, 2.00; S, 4.58. Found: C, 39.23; H, 2.29; N, 2.47; S, 4.62. MALDI-
X-ray Crystallography. Table S4 (Supporting Information)
reports details of the structural analysis for the complexes 4a, trans-
7c(dmso-κO), cis-8b and 8c. Red crystals of complex 4a were
obtained by slow evaporation at room temperature of a solution of the
complex in a 1:2 mixture of CH2Cl2 and hexane, while yellow (trans-
7c(dmso-κO), 8c) and orange (cis-8b) crystals were obtained by slow
diffusion of hexane into saturated solutions of the corresponding
compounds in acetone (trans-7c(dmso-κO), 8c, −30 °C) and CH2Cl2
(cis-8b, room temperature). X-ray intensity data have been collected
with a NONIUS-κCCD area-detector diffractometer, using graphite-
monochromated Mo Kα radiation (λ(Mo Kα) = 0.71071 Å), and the
images were processed using the DENZO and SCALEPACK suite of
programs.54 The structures were solved by Patterson and Fourier
methods using DIRDIF9955 (4a) or SHELXS-9756 (trans-7c(dmso-
κO), cis-8b and 8c) and refined by full-matrix least squares on F2 with
SHELXL-97.56 The absorption corrections were performed using
MULTI-SCAN,57 with the WINGX program suite.58 All non-
hydrogen atoms were assigned anisotropic displacement parameters.
The hydrogen atoms were constrained to idealized geometries fixing
isotropic displacement parameters of 1.2 times the Uiso value of their
attached carbons for aromatic and methylene hydrogens and 1.5 times
for the methyl groups. For complex 4a, the olefinic hydrogen atoms
H15 and H46 were assigned from the Fourier map and refined with a
fixed distance of 0.93 Å to their attached carbon atoms. Complexes 4a
and trans-7c(dmso-κO) crystallize with half a molecule of hexane
(4a·0.5(hexane) and trans-7c(dmso-κO)·0.5(hexane)), but we have
been not able to model the crystallization solvent present in the
structure of complex 8c. Examination with SQUEEZE59 revealed the
presence of two voids of 116 Å3 containing a total of 40 e, which fits
well for the presence in the unit cell of one molecule of acetone and
water. Therefore, we have included them in the empirical formula as
crystallization solvent (8c·0.25(acetone)·0.25H2O). For complex 4a,
five restraints have been used to model the hexane molecule found in
the asymmetric unit (4a·0.5(hexane)). The structures present some
residual peaks greater than 1 e Å−3 in the vicinity of the metal atoms or
solvent molecules, but with no chemical meaning.
1
TOF (+): m/z (%) 664 [M − Cl]+ (100), 631 [M − 2Cl]− (16). H
NMR (400.1 MHz, CDCl3, −30 °C, cis:trans isomers ∼7:1, δ): cis-8a
10.00 (d, J = 7.0, JPt−H = 20, H2, bzq), 8.54 (d, J = 8.0, H4, bzq), 7.96
(d, J = 8.4, H5/6, bzq), 7.90 (t, H3, bzq), 7.80 (m, H5/6, H7, bzq), 7.66
(t, J = 7.8, H8, bzq), 7.45 (t, J = 7.5, JPt−H = 35, H9, bzq), 3.16 (m, 1H,
α-CH2, tht), 2.96 (m, 1H, α-CH2, tht), 2.30 (m, 1H, α-CH2, tht), 2.07
(m, 1H, α-CH2, tht), 1.81 (m, 1H, β-CH2, tht), 1.48 (m, 2H, β-CH2,
tht), 1.15 (m, 1H, β-CH2, tht); trans-8a 9.08 (d, J = 4, H2, bzq), 8.45
(d, J = 10, H4, bzq), 8.00−7.46 (the rest of the bzq and tht signals are
overlapped with signals corresponding to cis-8a). 19F NMR (376.5
MHz, CDCl3, −30 °C, δ): cis-8a −110.4 (d, JPt‑oF = 75, 1o-F), −117.2
(d, JPt‑oF = 85, 1o-F), −156.8 (t, 1p-F), −159.7 (m, 1m-F), −161.8 (m,
1m-F); trans-8a −113.0 (m, JPt‑oF ≈ 80, 1o-F), −119.5 (d, JPt‑oF ≈ 85,
1o-F), −157.4 (t, 1p-F), −160.5 (m, 1m-F), −162.5 (m, 1m-F). A
1
sample was crystallized from CH2Cl2/Et2O giving rise pure cis-8a. H
NMR (400.1 MHz, CD3COCD3, −30 °C, δ): 10.03 (d, J = 8.0, JPt−H
=
20, H2, bzq), 8.94 (d, J = 8.0, H4, bzq), 8.18 (m, H5/6, H3, bzq), 8.11
(d, J = 12.0, H5/6, bzq), 7.95 (d, J = 8.0, H7, bzq), 7.71 (t, J = 7.5, H8,
bzq), 7.42 (t, J = 7.5, JPt−H = 35, H9, bzq), 3.08 (m, 2H, α-CH2, tht),
2.25 (m, 1H, α-CH2, tht), 1.74 (m, 2H, tht), 1.53 (m, 1H, β-CH2, tht),
1.02 (m, 1H, β-CH2, tht), 0.66 (m, 1H, β-CH2, tht).
Data for [Pt(bzq-κN,κC10)(C6F5)I2(tht)] (8b). [Pt(bzq-κN,κC10)-
(C6F5)(tht)] (3; 0.150 g, 0.238 mmol) and I2 (0.061 g, 0.238
mmol) were used to give 8b as an orange solid (0.126 g, 63%). IR
(cm−1): ν(C−F) 1078 (s), 970 (s); ν(C6F5)X‑sens 795 (s); ν(Pt−I) 224
(w). Anal. Calcd for C23H16I2F5NPtS: C, 31.31; H, 1.83; N, 1.59; S,
3.63. Found C, 30.89; H, 1.97; N, 1.67; S, 3.46. MALDI-TOF (+): m/
1
z (%) 755 [M − I + 2H]+ (100), 670 [Pt(bzq)(C6F5)I]+ (33). H
NMR (400.1 MHz, CDCl3, 25 °C, cis:trans isomers ∼5:1, δ): cis-8b
10.44 (d, J = 8.0, JPt−H = 16, H2, bzq), 8.46 (d, J = 8.0, H4, bzq), 7.97
(d, J = 8.0, H5/6, bzq), 7.78 (m, H5/6, H7, bzq), 7.73 (t, J = 7.5, H3,
bzq), 7.67 (t, J = 7.5, H8, bzq), 7.31 (t, J = 6.5, JPt−H = 38, H9, bzq),
2.86 (m, 2H, α-CH2, tht), 2.75 (m, 1H, α-CH2, tht), 1.78 (m, 1H, α-
CH2, tht), 1.55 (m, 2H, β-CH2, tht), 0.92 (m, 2H, β-CH2, tht); trans-
8b 9.33 (d, J = 5.0, JPt−H = 20, H2, bzq), 8.39 (d, J = 8.0, H4, bzq),
7.93−7.38 (the rest of the bzq and tht signals appear overlapped with
other corresponding to cis-8b). 19F NMR (376.5 MHz, CD3COCD3,
−50 °C, δ): cis-8b −92.2 (d, JPt‑oF = 109, 1o-F), −113.1 (d, JPt‑oF = 113,
1o-F), −159.6 (t, 1p-F), −162.9 (m, 1m-F), −164.3 (m, 1m-F); trans-
8b −101.4 (m, 1o-F), −105.2 (d, 1o-F), −160.8 (t, 1p-F), −163.7 (m,
1m-F), −165.5 (m, 1m-F). A sample was crystallized from CHCl3/n-
Computational Details for Theoretical Calculations. DFT
calculations were carried out using the Gaussian 09 package.60 All
calculations applied the functional of Perdew, Burke, and Ernzerhof61
that uses 25% exchange and 75% correlation weighting and is denoted
as PBE0. The basis set used was the LanL2DZ effective core
potential62 for the metal center (Pt) and 6-31G(d,p) for the ligand
atoms. All isomers were optimized without considering solvent effects,
and no negative values were found in the results of the vibrational
frequency analysis.
ASSOCIATED CONTENT
* Supporting Information
■
1
hexane to give mainly cis-8b. H NMR (400.1 MHz, CD3COCD3, 25
S
°C, δ): 10.36 (d, J = 8.0, JPt−H = 20, H2, bzq), 8.83 (d, J = 8.0, H4, bzq),
8.11 (m, H5/6, H3, bzq), 8.03 (d, J = 12.0, H5/6, bzq), 7.86 (d, J = 8.0,
H7, bzq), 7.71 (t, J = 8.0, H8, bzq), 7.30 (t, J = 7.5, JPt−H = 40, H9, bzq),
2.95 (m, 2H, α-CH2, tht), 1.87 (m, 1H, α-CH2, tht), 1.66 (m, 1H, α-
CH2, tht), 1.59 (m, 1H, β-CH2, tht), 1.40 (m, 1H, β-CH2, tht), 0.80
(m, 2H, β-CH2, tht).
1H NMR spectrum of 4b (Figure S1), molecular structure and
selected distances and angles for 4a (molecule B) (Figure S2
and Table S1), cyclic voltammetry of 1 (Figure S3), theoretical
calculations (Tables S2 and S3 and Figure S4), variable-
temperature 19F NMR spectra of 7a−c (Figures S5−S7),
3951
dx.doi.org/10.1021/om4004384 | Organometallics 2013, 32, 3943−3953

Organometallics
Article
variable-temperature 1H NMR spectra of 7a (Figure S8),
NOESY and NOE experiments for complex 7c at 223 K
(Figures S9 and S10), variable-temperature 19F NMR spectra of
8c (Figure S11), numbering Scheme for the bzq ligand (Figure
S12), and crystallographic data (CIF files and Table S4). This
material is available free of charge via the Internet at http://
pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E.L.: fax, (+34) 941 299 621; e-mail, elena.lalinde@unirioja.es.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Spanish MICINN (Project
CTQ2008-06669-C02-02/BQU). We thank the CESGA for
computer support.
́
(22) Díez, A.; Fornies
Inorg. Chem. 2005, 44, 2443. Díez, A.; Fornies, J.; García, A.; Lalinde,
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